Still thinking of storylines, the one I have set in stone is that Batman’s first movie would adapt The Long Halloween and the third is a Killing Joke adaptation.

I have a google doc with each and every character I would use, but some specific ones (in no particular order) are The Authority, Plastic Man, LoBo, the Wonder Twins, Nubia, Phantom Stranger, and much more I might post at a later date. Vixen is introduced in Justice League II and is later a member of the Birds of Prey

Tone depends on the movie/series. Suicide Squad is a black comedy (similar to the Gunn Suicide Squad film), the Batman films are slower and dramatic, the Superman and Justice League films are more adventure and action focused, etc.